Method for loading shape memory polymer gripper mechanisms

ABSTRACT

A method and apparatus for loading deposit material, such as an embolic coil, into a shape memory polymer (SMP) gripping/release mechanism. The apparatus enables the application of uniform pressure to secure a grip by the SMP mechanism on the deposit material via differential pressure between, for example, vacuum within the SMP mechanism and hydrostatic water pressure on the exterior of the SMP mechanism. The SMP tubing material of the mechanism is heated to above the glass transformation temperature (Tg) while reshaping, and subsequently cooled to below Tg to freeze the shape. The heating and/or cooling may, for example, be provided by the same water applied for pressurization or the heating can be applied by optical fibers packaged to the SMP mechanism for directing a laser beam, for example, thereunto. At a point of use, the deposit material is released from the SMP mechanism by reheating the SMP material to above the temperature Tg whereby it returns to its initial shape. The reheating of the SMP material may be carried out by injecting heated fluid (water) through an associated catheter or by optical fibers and an associated beam of laser light, for example.

[0001] The United States Government has rights in this inventionpursuant to Contract No. W-7405-ENG48 between the United StatesDepartment of Energy and the University of California for the operationof Lawrence Livermore National Laboratory.

BACKGROUND OF THE INVENTION

[0002] The present invention relates to the microgrippers, particularlyto shape memory polymer gripper/release mechanisms, and moreparticularly to a method and apparatus for loading shape memory grippermechanisms.

[0003] In recent years, substantial research and development has beendirected to microactuators, microgrippers, etc. particularly for medicalapplications and capable of operating in 250-500 μm diameterapplications, such as the blood vessels in the human body. Recently ashape memory polymer (SMP) material has been developed wherein above acertain temperature (Tc) the material becomes soft and can be shaped byapplying pressure, and cooling to a temperature below Tc, and uponreheating the material to a temperature above Tc the material returns toits original shape.

[0004] By the use of the SMP material, microgrippers have been developedfor applications such as depositing material (i.e., embolic coils) inthe blood vessels. Due to the capability of the SMP materials, a smallSMP tube attached to a guide wire or catheter is heated, an emboliccoil, for example, is inserted in the tube, and pressure is applied tothe SMP material causing it to conform about the coil, whereafter theSMP material is cooled thereby freezing the SMP material in the formedshape thereby gripping the coil, and upon reheating the SMP material thematerial returns to its original shape thereby releasing the coil. SuchSMP microgrippers are described and claimed in copending U.S.application Ser. No. 08/807,412 filed Feb. 28, 1997, entitled,“Microfabricated Therapeutic Actuators”, and assigned to the sameassignee.

[0005] The present invention involved the loading of the SMP tubing withdeposit material for medical applications, such as an embolic coil,medication, etc., and for non-medical applications requiring thedelivery and release of components in normally inaccessible areas. Theapparatus of the present invention operates via differential pressurebetween vacuum and hydrostatic water pressure whereby an application ofuniform pressure on the exterior of the SMP tubing, with a vacuum on theinterior thereof causes heated SMP tubing to change shape and grip adevice located therein, after which the SMP tubing is cooled and therebyfreezes in its changed shape. The heating and the cooling of the SMPtubing can be accomplished by the water utilized to produce the pressurefor changing the shape of the SMP tubing. The heating of the SMP tubingmay also be accomplished using optical fibers and laser light. Also,either heated water passing through a catheter to which the SMP tubingis attached or laser light via optical fibers packed to the SMP tubingmay be utilized to reheat the tubing and release the device therefrom.

SUMMARY OF THE INVENTION

[0006] It is an object of the present invention to enabling loading ofshape memory polymer material with a deposit material.

[0007] A further object of the invention is to provide a method forloading a shape memory polymer tubing with a device to be gripped andreleased thereby.

[0008] A further object of the invention is to provide a loadingmechanism for shape memory polymer gripper/release mechanisms.

[0009] Another object of the invention is to enable loading of a shapememory polymer gripper/release mechanism utilizing differential pressureon the external and internal areas of the shape memory polymer material.

[0010] Another object of the invention is to provide loading of a shapememory polymer tube with a device to be gripped/released thereby,utilizing differential pressure between vacuum and hydrostatic waterpressure.

[0011] Another object of the invention is to provide loading of a shapememory polymer gripper/release tubing utilizing pressured water which isheated and cooled on the external area of the tubing while drawing avacuum in the internal area thereof, and applying a mechanism to areasof the heated external area of the tubing to form depressions thereinwhich are frozen in the tubing by cooling of the external area.

[0012] Another object of the invention is to provide loading for a shapememory polymer gripper/release tubing utilizing laser heating of thetubing and differential pressure and cooling for forming depressions inthe tubing for gripping a device positioned therein.

[0013] Other objects and advantages will become apparent from thefollowing description and accompanying drawing. The invention involvesthe loading of a shape memory polymer SMP gripper/release mechanism witha device to be gripped and released. The invention is carried out byinserting in an SMP tubing a device to be gripped/released, utilizingdifferential pressure between the internal and external areas of a SMPtubing after and/or during the heating of the tube whereby depressionsare formed in the tubing, and thereafter cooled the tubing causing afreezing of the thus formed depressions in the tubing which causesgripping of the device located in the tubing. Release of the device fromthe SMP tubing is accomplished by reheating the tubing such that itreturns to its original shape. The method and apparatus of thisinvention requires the use of an SMP tubing having a glasstransformation temperature (Tg) which when heated above Tg can bereshaped, and subsequent cooling below Tg freezes to tubing in itsreshaped configuration. The heating and/or cooling can be provided bythe same water applied for pressurization, or the heating can beprovided by optical fibers packaged with the SMP tubing via which laserlight, for example, is directed onto the tubing. The heating and coolingmay be carried out during pressurization of the tubing by controllingthe temperature of the water used in the differential pressureapplication to the tubing.

BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The drawings, which form a part of the disclosure, illustrate themethod and apparatus of the invention, and together with thedescription, exemplify and teach the principles of the invention.

[0015]FIG. 1 is a partial cross-sectional view of an embodiment of aloaded shape memory polymer gripper/release mechanism which has beenloaded in accordance with the present invention.

[0016] FIGS. 2-5 illustrate the method for loading the gripper/releasemechanism of FIG. 1.

[0017]FIG. 6 illustrates schematically and in partial cross-section anembodiment of the differential pressure apparatus for loading a shapememory polymer tubing in accordance with the invention.

[0018]FIG. 7 illustrates schematically and in partial cross-sectionanother embodiment of the loading apparatus, similar to FIG. 6, bututilizing laser light via optical fibers for heating the tubing, forboth gripping and releasing a deposit material.

[0019] FIGS. 8-11 illustrate embodiments of loading mechanisms utilizingmechanical pressure to load a shape memory polymer tubing.

DETAILED DESCRIPTION OF THE INVENTION

[0020] The present invention is directed to loading shape memory polymergripper/release mechanisms with a deposit material. The inventioninvolves a method and loading apparatus to enable gripping and releaseof a deposit material utilizing a shape memory polymer (SMP) tubing andheating the tubing to be above the glass transformation temperature (Tg)while reshaping the tubing via differential pressure, and subsequentlycooling the tube to below the Tg to freeze the shape. Upon reheating theSMP tubing to a temperature above the Tg it returns to its originalshape. Thus, by utilizing the SMP tubing as a gripper/release mechanism,it can be utilized for gripping/releasing devices such as embolic coils,medicine, etc. at a point of use as described and claimed inabove-referenced application Ser. No. 08/807,412. The loading of the SMPgripper/release mechanism is carried in accordance with the presentinvention by utilizing a differential pressure between the interior andexterior of the heated SMP tubing. For example, the differentialpressure between vacuum on the interior of the tubing and hystrostaticwater pressure on the exterior of the tubing is used to formindentations in the SMP tubing which function to grip a devicepositioned in the tubing. Also, by applying vacuum to the interior,mechanical pressure can be applied to the exterior. In addition, thewater utilized to produce the hydrostatic pressure on the tubing can beheated to cause the tubing temperature to raise above the Tgtemperature, and the same water can be cooled to cool the tubing tobelow the Tg temperature which results in a freezing of the tubing inits reformed shape. Also, controls may be utilized to enablesimultaneous heating and pressurization of the water, and/orsimultaneous pressurization and cooling to enable a continuous heating,pressurization, and cooling sequence. Also, instead of utilizing waterto heat the SMP tubing, laser light may be directed into the interior oftubing via optical fibers. Either laser light or warm water may be usedto reheat the SMP tubing above its Tg temperature to allow it to returnto its original shape and to release any device previously grippedtherein. The apparatus of the present invention enables the applicationof uniform pressure to secure a grip on a deposit material viadifferential pressure.

[0021] In addition to medical applications for depositing materials inblood vessels in the human body, having a 250-500 μm diameter, the SMPgripper/release mechanism can be used for various non-medicalapplications, such as assembly of read-write heads for disk drives andother microassembly applications.

[0022] As pointed out above, the SMP gripping principle is based on theunique property of the shape memory polymer. This polymer possesses aglass transformation temperature (Tg) above which the material enters areversible glassy phase where it becomes soft and flexible and easy toreshape. Once reshaped and cooled below Tg, the new shape is frozen inplace and the material becomes hardened to over five (5) times theelastic modules of the glassy phase. Upon reheating the material to atemperature above Tg it returns to its original shape. By way ofexample, the Tg of the SMP material is in the range of 25 to 75° C., andthe material may be manufactured to produce a Tg anywhere in this range.In the SMP tubing utilized to experimentally verify the presentinvention the SMP tubing, manufactured by Mitsubishi, had a Tg of 55° C.

[0023] Prior to a detailed description of the method and apparatus ofthe present invention, a broad description thereof is as follows: First,the SMP tubing, which may be retained at the end of catheter, guidewire, or optical fiber, as illustrated in the drawings, will be heatedabove its transformation temperature Tg by, for example, warm water, asshown in FIG. 6, or laser light via an optical fiber, as shown in FIG.7, and will become soft for conforming to gripped configurations, suchas shown in FIGS. 1, 6, and 7. then the loading mechanism (see FIGS. 6and 7) will provide a force to conform the SMP tubing about a depositmaterial or device, such as an end of an embolic coil. The loadingapparatus is operated by providing a pressure difference inside andoutside of the SMP tubing, for example, either by providing vacuum tothe inside or hydrostatic pressure to the outside, or both. As thepressure is applied, the SMP tubing conforms into or partially intogrooves in the device positioned therein and provide a packaged lockingconfiguration. At this point, the warm water or laser light heating isreplaced with cold water or other cooling means to cool the SMP tubingbelow the Tg to freeze it into the locking configuration. In the loadingapparatus illustrated in FIGS. 6 and 7, a plurality of movable memberscontaining O-rings are utilized to provide a sealed compartment forwater to produce heating/cooling for conforming of the SMP tubing asdescribed in detail hereinafter. These movable members may be located onopposite sides of the tubing, or spaced around tubing so that pressurethereon, such as hydrostatic water pressure moves the members intocontact with the tubing and the water pressure passing through openingsin the members form indentations in the tubing to secure the depositmaterial or device therein. In addition to the use of water to heat,pressurize and cool the SMP tube, the water can be used to heat and coolthe tubing and mechanical pressure can be used to move the membersagainst the outer surface of the SMP tube, with or without a vacuumwithin the tubing. Also, a combination of laser light heating and watercooling can be utilized with either hydrostatic water or mechanicalpressure being applied to conform the tubing about a device therein.FIGS. 8-10 illustrate mechanical arrangements for conforming the SMPtubing about a device to be retained therein.

[0024] Referring now the FIGS. 1-5, wherein FIG. 1 illustrates anembodiment of a shape memory polymer (SMP) gripper/release mechanism,made by the method schematically illustrated in FIGS. 2-5. The methodfor producing the embodiment of FIG. 1, as illustrated in FIGS. 2-5 isexemplified as follows:

[0025] 1. Heat is applied to an SMP tubing 10, having a glasstransformation temperature of 35-65° C., as indicated by legend andarrows 11 in FIG. 2 to a temperature above Tg. The heat may be producedby a fluid such as hot water, gas, oil, etc., having a temperature of 45to 65° C., applied to the external surface 12 of tubing 10, or by laserlight transmitted to the interior surface 13 of tubing 10 via opticalfibers adapted to be positioned in an opening 14 of a tube 15, securedin one end 16 of tubing 10. The optical fibers may replace the tube 15.By way of example, the tubing 10 may have an internal diameter of 200 μmto 1000 μm and an external diameter of 250 μm to 1050 μm. The tube 15may be replaced with a solid guide wire.

[0026] 2. An end section 17 of a deposit material 18, such as an emboliccoil, is inserted through an end 19 of tubing 10 into the interior ofthe tubing 10, as shown in FIG. 3, with end section 17 provided with onegroove or a plurality of spaced grooves 20. If desired the end section17 can be inserted prior to heating the tubing. The external diameter ofend section 17 being slightly smaller than the internal diameter oftubing 10 so as to provide easy insert of the end section 17 into tubing10. By way of example, the grooves 20 may have a width of 25 μm to 200μm and diameter of 150 μm to about 500 μm, and spaced about a distanceof 50 μm to 150 μm, with end section 17 having an external diameter of180 μm to about 500 μm.

[0027] 3. Pressure is applied to the external surface of heated tubing10 as indicated by legend and arrows 21 in FIG. 4, while a vacuum isdrawn on the internal surface 13 of tubing 10 as indicated by legend andarrows 22. The pressure 21 may be produced by hydrostatic water, gas, oroil pressure or mechanical pressure. The vacuum 22, produced by a pump,not shown, may be at a Torr of 10⁻⁴ to 1. If produced by hystrostaticpressure, the water used to heat the tubing 10 may be pressurized to apressure of 800 to 3000 Torr. As seen in FIG. 4, the pressure on heatedtubing 10 causes sections of the tubing adjacent grooves 20 of endsection 17 to conform or indent as indicated at 23. While not shown inFIG. 4, heat 11 may be applied to tubing 10 simultaneously with pressure21 to maintain the tubing 10 soft and pliable. Also, pressure 21 may beapplied without vacuum 22 but such decreases the differential betweenthe external and internal surfaces of tubing 10 and thus the externalpressure would need to be increased to produce the same results. Theindentations 23 provide a locking between tubing 10 and end section 17.

[0028] 4. The tubing 10 is cooled as indicated by legend and arrows 24,as shown in FIG. 5, to a temperature below Tg, whereby the indentations23 are frozen, and the indentations 23 of tubing 10 remain in theirlocked position within grooves 20 of end section 17. The cooling 24 maybe carried out using cold water or other cooling means (gas, oil, etc.),and can be carried simultaneously with pressure 21 remaining applied. Ifcooling 24 is carried out by water, a water temperature of 5 to 25° C.may be used, and the cooling water may be the same as used for heatingtubing 10 and/or for producing the hystrostatic pressure 21. Uponcooling of the tubing 10, an SMP gripper/release mechanism 25, asillustrated in FIG. 1, is produced, wherein end section 17 of thedeposit material 18 is gripped by tubing 10 which is attached to tubing15, which may, for example, be attached to a catheter or guide wire forinsertion into a blood vessel of a human body, or a guide wire may beutilized in place of tubing 15 to insert the gripper release mechanism25 and a deposit material 18 into a non-medical inaccessible area.

[0029] Upon the SMP gripper/release mechanism and loaded depositmaterial be positioned by the guide wire at a point of use, the SMPtubing 10 is heated to a temperature above the Tg of tubing 10, whichallows the tubing 10 to revert to its original configuration therebyremoving the indentations 23 in tubing 10 allowing the end section 17 ofdeposit material 18 to be released up removing the tubing 10 from thearea of use of the deposit material 18. Reheating of the tubing 10 toabove it temperature Tg can be carried out, for example, by injectinghot water through the opening 14 of tubing 15 into the interior oftubing 10, or by directing laser light via optical fibers in opening 14of tubing 15 into the interior of tubing 10. Also, a solid guide wirewith optical fibers wrapped therearound may be utilized in place oftubing 15.

[0030]FIG. 6 illustrates schematically an embodiment of a loadingmechanism utilizing differential pressure involving hydrostatic pressureand vacuum on the exterior and interior of the SMP tubing. Componentscorresponding to components of the FIG. 1 embodiment will be givencorresponding reference numerals. As shown, an end section 17 of adeposit material 18 is positioned in an SMP tubing 10 secured at one endto a guide wire or optical fiber 15′, the end section 17 including aplurality of spaced grooves 20. In this embodiment arrows 11/21/24 areutilized to indicate heating of, pressure on, and cooling of the SMPtubing 10, as in the operational sequence described above with respectto FIGS. 2 and 5, using water to apply the pressure (21) and warm waterfor heating (11), or cold water for cooling (24). A pressuredifferential loading mechanism generally indicated at 30 comprises aplurality of members positioned about the SMP tubing 10, two members 31and 32 being illustrated in this embodiment, with members 31, 32 beingprovided with openings 33 to allow passage of heating/pressure/coolingwater as indicated by arrows 11/21/24. Each of members 31-32 is providedwith at least one groove 34 in which flexible members or O-rings 35 and36 are retained around SMP tubing 10. As differential pressure indicatedby arrows 21′ is applied against the members 31-32 and a vacuum 22 isdrawn on the interior of tubing 10, the flexible members or O-rings 35and 36 are pressed against the external surface of heated SMP tubing 10producing indentations 23′ in the tubing, and forming a seal around thetubing 10 which defines a compartment or area 37 between O-rings 35-36and between tubing 10 and members 31-32. As pressurized fluid (water)flows through opening 33, indentations 38 are formed in tubing 10 whichprovide locking between the SMP tubing 10 and the end section 17 of thedeposit material 18. As described above, the pressure 21′ on members31-32 can be maintained during cooling. Note that the sealingindentations 23′ in FIG. 6 have been illustrated as not extending intothe grooves 20 of end section 17 while indentations 38 extend intogrooves 20. The location of the indentations 23′ and 38 with respect tothe grooves 20 of end section 17 is dependent on the location of endsection 17 within SMP tubing 10 and the location of the flexible membersor O-rings 35-36.

[0031] Various modification of the loading apparatus 30 may be utilized.For example, the members 31 and 32 may be provided with a plurality ofopenings therein to provide for passage of heating/cooling water. Also,there may be a plurality of loading members located in spaced relationaround the SMP tubing so that the sealing indentations 23′ extendsaround the tubing. The spacing of the loading members must be such as toallow movement thereof by hydrostatic pressure, for example, or bymechanical pressure if desired, to produce the desired sealingindentations in the SMP tubing. In addition, if desired, additionalflexible members or O-rings, such as shown at 35 and 36 located inadditional grooves in members 31-32 may be utilized to form additionalcompartments or areas therebetween. Also, instead of flexible members orO-rings, balls secured in the grooves of the members 31-32 may beutilized to mechanically provide tubing indentations as shown in FIG. 8.Also, forming protruding sections on the members 31-32 in place of thegrooves and flexible members or O-rings may be utilized to produce thedesired indentations in the heated SMP tubing.

[0032]FIG. 7 illustrates a loading mechanism similar to that of FIG. 6except that heating of the SMP tubing is carried out by directing laserlight into the interior of the tubing via optical fibers. In FIG. 7, theend section of the deposit material is shown only partially insertedinto the SMP tubing to enable dearer illustration of the laser beamheating the SMP tubing. Components similar to the components of FIG. 6are given corresponding reference numerals. As shown, an optical fiber40 positioned in opening 14 of tubing 15 is secured to one end of SMPtubing 10. A plurality of optical fibers 40 may be utilized. Laser lightindicated at 41 is passed through optical fiber 40 into the interior 42of SMP tubing 10 for heating the tubing to a temperature above the Tg,as described above. In this embodiment, as in FIG. 6, the end section 17of the deposit material may be inserted into the SMP tubing after orprior to heating of the tubing. However, where laser light is utilizedto heat the tubing it is more efficient to only partially insert the endsection prior to heating, as shown in FIG. 7, whereby the laser lightwill bounce off the end of the end section 17 rather than passing outthe end of the SMP tubing, thereby providing more efficient heating. Byway of example the laser light 41 may be at a wavelength of 400 nm to1000 nm. As pointed out above, a solid guide wire with optical fiberwrapped around or along the external surface thereof may be utilized inplace of tubing 15 with optical fiber 40 therein.

[0033] After heating of the SMP tubing 10 by laser light as shown inFIG. 7, and the end section 17 of the deposit material is inserted intothe SMP tubing, as in FIG. 6, the operation of the loading mechanism 30as described above with respect to FIG. 6 is carried out to produce andfreeze the indentations 38 in SMP tubing 10, not shown in FIG. 7.

[0034] While not shown, the hydrostatic water pressure 21, as well asthe heating water and/or cooling water, may utilize the same water whichflow is controlled and passes through a heating means, a pressurizingpump, and a cooling means, or means for a heating/pressurizationoperation and/or a pressurization/cooling operation. Such controlledsystems can be readily utilized using computer control known in the art.Such heating/pressurization/cooling operations can be carried out in acontrolled sequence to enable efficient manufacturing of shape memorypolymer gripper/release mechanisms in various sizes and for variousapplications.

[0035]FIG. 8 illustrates a loading apparatus generally similar to FIG. 6except that the indentations in the SMP tubing are formed mechanicallyinstead of hydrostatically. Similar components to those of FIG. 6 aregiven corresponding reference numerals. The only structural differencefrom the FIG. 6 embodiment is the replacement of the flexible members orO-rings with a plurality of ball, only four (4) such balls being shownin FIG. 8 at 50-53. As in the FIG. 6 embodiment, warm or cold waterindicated by arrows 11/24 is utilized to heat and/or cool the SMPtubing, but mechanical pressure indicated by arrows 21′ in FIG. 8 isused to form indentations 23′, the only indentations formed in SMPtubing 10. The depth of the indentations 23′ is dependent on therelative location of balls 50-53 with respect to grooves 20 in endsection 17 of deposit material 18. As shown in FIG. 8, the indentations23′ are sufficient to retain the end section 17 within SMP tubing 10,even though such do not fully extend into grooves 20 of end section 17as does indentations 38 in the FIG. 6 embodiment. The mechanicalpressure 21′ on members 31 and 32 may be provided by conventional presstechnology, for example. While only four (4) balls 50-53 are shown,grooves 34 in members 31 and 32 may contain any desired number of balls,each forming an indentation 23′ in the SMP tubing 10 when pressure 21′is applied.

[0036]FIG. 9 illustrates a loading apparatus utilizing a mechanicalclamp arrangement. In this embodiment of an apparatus generallyindicated at 30′, a coil or deposit material 18 is positioned in a SMPtubing 10, as in FIG. 6, and a pair of mechanical clamps 60 and 61having liners or members 62 and 63, constructed of a polymer or high CTEmaterial, which are forced against the heated SMP tubing 10 when thedamps 60 and 61 are forced toward each other causing indentations in theheated SMP tubing 10, the pressure on the clamps 60 and 61 beingmaintained until the SMP tubing 10 has cooled below the Tg temperaturethereof, whereby the indentations are frozen in the SMP tubing until itis reheated above its Tg, and the pressure on the clamps 60-61withdrawn. Movements of the clamps 60-61 being shown by double arrow 64.The liners members 62 and 63 may be of a variety of configurationsincluding spaced sections, protruding sections, etc., and located toform indentations at any desired location on the deposit material orcoil 18 so as to retain same within the cooled SMP tubing 10.

[0037]FIG. 10 schematically illustrates a loading mechanism usingmechanical damping with alignment pins. In this arrangement an SMPtubing 70 is secured at one end to a guide wire, optical fiber orcatheter 71, with an end 72 of a deposit material 73 being inserted intoan opposite end of SMP tubing 70, by a retain means 74. The loadingmechanism comprises a pair of annular matching spaced members, only aportion of each pair shown at 75 and 76 and having openings 77 and 78,respectively, within which the SMP tube 70 and the end 72 of depositmaterial 73 are inserted, with opening 78 being of a smaller diameterthan opening 77. Members 75 and 76 additionally include openings 79-80and 81-82 through which alignment pins 83 and 84 are inserted to alignmembers 75 and 76, which are spaced from each other to definecompartments or areas 85 and 86. Member 76 is provided with a taperedsurface 87 adjacent opening 78.

[0038] In operation of the FIG. 10 mechanism, pressure is applied to thepairs of members which cause member 75 and tapered surface 87 of member76 to contact the SMP tubing 70 forming a seal therebetween whereafterfluid pressure indicated by arrows 88 is directed through compartmentsof areas 85 and 86 causing an end 89 of the SMP tubing 70 to conform tothe shape of the end 72 of deposit material 73, and upon cooling the SMPtubing 70 as described above, the end 72 of deposit material 73 isretained within the end 89 of SMP tubing 70. However, pressure appliedby the tapered surface 87 may be utilized as a clamping surface to causethe end of 89 of tubing 70 in conforming to the shape of the end 72 ofdeposit material 73.

[0039]FIG. 11 illustrates an inverted version of the loading mechanismof FIG. 10, the difference being that the end 72′ of deposit material 73is inserted into the end 89 of SMP tubing 70, thus eliminating theretainer mechanism 74 of FIG. 10, whereafter the SMP tubing 70 and thedeposit material 73 are inserted through opening 77 of member 75 andinto opening 78 in member 76 as indicated by arrow 90 until the end 89of SMP tubing contacts tapered surface 87 of member 76, whereafterpressure fluid is directed into areas 85 and 86 causing the end 89 ofSMP tubing 70 to fully conform to the external surface of end 72 ofdeposit material 73, as described above. In the FIG. 11 embodiment theinitial I.D. of SMP tubing 70 is slightly greater than the O.D. of theend 72 of the deposit material 73 so that the deposit material isinitially retained in the end of the SMP tubing 70 by the close fit.

[0040] It has thus been shown, that the present invention provides amethod and apparatus for loading shape memory polymer (SMP)gripper/release mechanism. The invention utilizes differential pressure,such as between vacuum and hydrostatic water pressure, to produceindentations in SMP tubing for retaining deposit material therein. Theinvention utilizes heated water or laser light to heat the SMP tubing,and water to cool the tubing after the indentations are formed to freezesame in a locking position about the deposit material. The same watermay be utilized for heating, pressurization, and cooling of the SMPtubing. The invention enables the efficient and inexpensive manufactureof SMP gripper/release mechanisms for various applications, particularlythose requiring operation in areas of 250-500 μm diameters.

[0041] While particular embodiments of the invention have beenillustrated and/or described and particular operational sequences havebeen described, along with exemplary parameters, materials, etc., suchare not intended to be limiting. Modifications and changes may becomeapparent to those skilled in the art, and it is intended that theinvention be limited only by the scope of the appended claims.

The invention claimed is:
 1. An apparatus for loading a shape memorypolymer gripper/release mechanism, comprising: means for heating theshape memory polymer having a configuration; means for applying pressureto the heated shape memory polymer to cause a change in theconfiguration of the shape memory polymer; and means for cooling theshape memory polymer to maintain the configuration of shape memorypolymer caused by applying pressure thereto.
 2. The apparatus of claim 1, wherein the means for applying pressure includes means for producing adifferential pressure on the shape memory polymer.
 3. The apparatus ofclaim 2 , wherein the means for producing differential pressureincluding a vacuum and a hydrostatic or mechanical pressure.
 4. Theapparatus of claim 3 , wherein said shape memory polymer is of a hollowconfiguration, and wherein said differential pressure is applied bymeans across at least a portion of a wall surface forming the hollowconfiguration.
 5. The apparatus of claim 4 , wherein the differentialpressure is produced between vacuum means and hydrostatic water pressuremeans.
 6. The apparatus of claim 5 , wherein the vacuum means is appliedto an interior of said hollow configuration and said hydrostatic waterpressure means is applied to an exterior of said hollow configuration.7. The apparatus of claim 1 , wherein said means for applying pressureincludes a plurality of members having means for at least formingindentations in said shape memory polymer.
 8. The apparatus of claim 7 ,wherein said plurality of members are moved against a surface of saidshape memory polymer by means forming a differential pressure.
 9. Theapparatus of claim 1 , wherein said means for applying pressure includesa plurality of flexible members at least forming spaced seals about saidshape memory polymer.
 10. The apparatus of claim 9 , wherein said spacedseals form an area about said shape memory polymer into which fluidpressure is directed to form at least one indentation in said shapememory polymer.
 11. The apparatus of claim 1 , wherein said heatingmeans is selected from the group selected from heated fluid and laserlight.
 12. The apparatus of claim 1 , wherein said heating means, saidpressure applying means, and said cooling means each include a quantityof fluid.
 13. The apparatus of claim 12 , wherein said heating means,pressure applying means, and said cooling means includes the same fluid.14. The apparatus of claim 11 , wherein said heating means includes atleast one optical fiber for directing laser light onto said shape memorymaterial.
 15. The apparatus of claim 14 , wherein said shape memorypolymer is of a tubular configuration and said laser light is directedinto an interior of said tubular configurations.
 16. The apparatus ofclaim 1 , wherein said cooling means includes a quantity of cooled watercapable of cooling the heated, pressurized shape memory material to atemperature below a phase transformation temperature of said shapememory polymer.
 17. A method for loading a shape memory polymer to forma gripper/release mechanism retaining a deposit material, including:heating a quantity of shape memory polymer, having at least a section ofa deposit material located therein, to a temperature above atransformation temperature of the shape memory polymer; applyingdifferential pressure across the heated shape memory polymer causing achange in the shape memory polymer configuration; and cooling the shapememory polymer to a temperature below the transformation temperature tomaintain the change in the configuration of the shape memory andmaintain at least contact between the shape memory polymer and at leasta portion of the section of deposit material therein for retaining atleast the section of deposit material in the shape memory material. 18.The method of claim 17 , additionally including heating the shape memorypolymer and then inserting at least the section of deposit materialtherein.
 19. The method of claim 17 , wherein heating the shape memorypolymer is carried out, using heated fluid or laser light.
 20. Themethod of claim 17 , wherein applying a differential pressure is carriedout between a vacuum and hydrostatic fluid pressure.
 21. The method ofclaim 17 , wherein cooling the shape memory polymer is carried out usingcool fluid.
 22. The method of claim 17 , additionally includingattaching the shape memory polymer to a guide wire.
 23. The method ofclaim 17 , wherein applying a differential pressure is carried out usingat least mechanical pressure, and utilizing means for causing the changein shape of the shape memory polymer.
 24. The method of claim 17 ,wherein the change in shape of the shape memory polymer is carried outby forming spaced seals about the shape memory polymer, and directingpressurized fluid onto the shape memory polymer intermediate the spacedseals.